4.3. Parameter Connection for Synchronization

Besides data connections between module inputs and outputs (Image, Inventor, and Base connectors) it is also possible to connect module fields via a parameter connection. The values of connected fields are synchronized, that means when changing the value of one field, all fields connected to this field will be adapted to the same value.

Some important points:

In our example, a bidirectional parameter connection is the way to synchronize the View2D modules so that the same slice is rendered in both viewers. To establish this, proceed as follows:

  1. Add a SyncFloat module to the network and open its panel with a double-click.

  2. Right-click each View2D module to open the context menu and select Show WindowAutomatic Panel (alternatively, press ALT and double-click the module). The field that controls the currently rendered slice in a SoView2D module is the startSlice field.

  3. On the SoView2D panel, select the label of the startSlice field and drag the (invisible) connection onto the label of startSlice field on the SoView2D1 panel. The connection is drawn as thin gray arrow with the arrowhead pointing to the module that receives the parameter as input.

  4. In the other direction drag the startSlice field from the SoView2D1 panel to the float1 field of the SyncFloat panel, and from the same panel the float2 field to the startSlice field of the SoView2D panel. The intermediate SyncFloat module breaks the inevitable notification loop by only triggering the second connection at real value changes.


Another typical way of notating the fields is “InstanceName.FieldName”, for example SoView2D.startSlice. You will find this notation when you right-click the parameter connection to open its context menu, in which you can disconnect single or all parameter connections.

Figure 4.9. Establishing the Parameter Connections

Establishing the Parameter Connections

Figure 4.10. Resulting Network

Resulting Network

As a result, moving through the slices with the mouse wheel (“slicing”) in one of the viewers synchronizes the rendered slice in the second viewer.


A list of all parameter connections is displayed in the Parameter Connections Inspector View (which can be opened via the menu bar, ViewViewsParameter Connections Inspector). Right-click the connections for a context menu with various options.

For further information on parameter connections, please refer to the MeVisLab Reference Manual.

This is the end of this example. The full network is delivered with the demos of MeVisLab (available via HelpWelcomemore...ContourFilter.mlab).